Dimerization of alpha-alkyl para-alkyl styrenes



Patented Sept. 28, 1948 2,450,027 DIMEBIZA'I'ION F ALPHA-514K114PABA-ALKYL STYB Arthur J. Warner, South Orange,

1!. Talbot, East Orange, eral Telephone and Radio Corporation, New York,N. Y., a corporation of Delaware No Drawing. Application December 21,194:, Serial No. 515,188

8 Claims.

This invention relates to the dimerization' of alpha-alkyl para-alkylstyreneaand to the products thereof;

A feature of the invention is the production of said dimers in anexceptionally pure and homogeneous form which has unusual and unexpectedcharacteristics. The products arev substantially diiferent from thoseheretofore made by methods employing sulfuric acid as a catalyst; and itis believed that said methods in fact produce a substance including aconsiderable proportion of compounds other than said dimer which mate'-rially affect its properties and introduce variations and uncertainty inthe physical characteristics of said product. The dimers obtained inthis manner, when separated from solvents and diluents. are believed toinclude a considerable proportion in solid form and thereforesubstantially diiferent from the dimers produced in accordance withthisinvention.

The general purposes of the invention include the production ofsubstantially pure dimers of alpha-alkyl para-alkyl styrenes, thedevelopment of a process which will result in a man yield of said dimersand the provision of a reaction which can be' completed very rapidly,thereby en hancing materially the commercial value and practicability ofthe process.

The invention includes a process in which activated impure kaolin.particularly fullers earth or similar bleaching earths are employed ascata lysts. when such earths are used as polymerization catalysts forsubstances of the indicated type without special preparation orregulation, they are relatively ineffective, and in particular theresults obtained vary widely and the yields, are relatively low. Afeature of the invention is the preparation 'of the fullers earth byactivation at a relatively high temperature. This treatment produces anefficient catalyst with which'rapid reaction and high yields of thedimers can be ob tained.

It has been found that the variety of fullers earth from'Florida knownas floridin is especial-'- ly eflective as a catalyst. In order toprepare it for use it should be heated to a temperature be-' tween 200;C. and 400 0.. and preferably between 825 C. and 375 C., the optimumtemperature bemg 350? C. The catalyst will be properly activoted byheating at the required temperature for about twohours, or longer ifdesired.

It has been found that the temperature to which the floridin is heatedis of substantial importance in this process having an unexpected effect.on the rate of reaction and the percentage of yield of the desireddimer. This result is apparently due to dehydration of the earth, andtherefore the time and temperature of activation should be sufficient todrive of! water which is present in combination in such earth.

ENES

and Theodore N. 5., allignors to Fed- The proportion of catalystemployed also has an important bearing on the efliciency of the process.A minimum amount of /2 should be us and the maximum amount should notexceed 10%, the optimum range being between 2% and 5%. It'has been foundthat there is an intimate relationship between the percentage of thecatalyst and the starting temperature of the reaction if maximum yieldis to be obtained. For instance. in making the dimer of alpha-methylpara-methyl styrene, the starting point should be at least 60 0.. and atemperature in the range between 90*"6. and 100 C. is most advantageousis kept at least slightly below when the catalyst is used in aproportion between 2% and 5%. The upper limit of the startingtemperature is the boiling point. and it preferably the boiling point,that is, sufliciently below said point to avoid the danger that thetemperature may unintentionally rise above boiling, since it has beenfound that in order to produce the liquid dimers of the type indicatedherein, boiling should be avoided. The optimum starting temperaturerange for different alpha-alkyl para-alkyl styrenes will maintain arelationship to the boiling point similar to that given above foralpha-methyl para-methyl styrene.

A feature of the invention is the rapidity with which the reaction takesplace, generally within a few minutes. This is in marked contrast toprocesses such as those employing sulfuric acid catalysts, whichfrequently require hours to complete the polymerization. Moreover, theyield of the dimer is, in most cases, very high, and it is obtained in avery pure form, which can readily be separated from the exact time ofreaction may vary somewhat with different styrene derivatives of theindicated type and different conditions of reaction; but its conclusionfor any given materials and conditions can readily be determined by thestabilization of the refractive index.

After the dimerization is ended the catalyst is removed in any desiredmanner, as by filtration or centrifuging, and the dimer is separated bytractional distillation from the other constituents. which ordinarilywill consist of a small amount of higher polymers and a small residue ofthe monomer.

The process is eifective for producing dimers of the alpha-alkylpara-allryl styrenes which do not have more than five carbon atoms ineither subst-ituent. For instance, the process can be used for obtainingthe dimers of alpha-methyl paramethyl styrene, alpha-ethyl para-ethylstyrene, alpha-propyl para-propyl styrene, alpha-butyl para-butylstyrene and alpha-amyl para-amyl styrene. It is also effective forobtaining dimers of the alpha-para styrenes which have carbon sidechains of different lengths, such as alpharemaining constituents.Theuses which illustrate the invention.

Example 1 500 grams of crude monomeric alpha-methyl para-methyl styrenehaving a refractive index No 1.5337 was reacted with 2% of activatedfuller's earth at an initial "reaction temperature of 100 C.. reaching amaximum temperature'of 141 and a. maximum refractive index Nn'" 1.5580in 5 minutes, when the reaction was terminated. Fractional distillationseparated a substantially pure dimer of alpha-methyl parametbyl styrenerepresenting a yield of about 81%, a monomenic fraction of about 14% anda fraction including higher polymers tota ling about 8%.

Example 2 44.5 grams of crude monomeric alpha-methyl para-ethyl styrenehaving a refractive index Nn 1.5130 was reacted with 4.6% of activatedfullers earth at an initial reaction temperature of 180 C, reaching arelatively stable refractive index Nn= 1.5200 after 63 minutes, when thereaction was complete. Fractional distillation separated a substantiallypure dimer of alphamethyl para-ethyl styrene representing a yield of amonomeric fraction of 79% and a fraction including higher polymerstotaling 9%.

The resulting dimers of the alpha-alkyl paraalkyl styrenes aresubstantially colorless liquids of low viscosity, free from unpleasantodor and having high boiling points and low freezing points, the boilingpoints being above 300 C. while the freezing points are C. and lower.Their densities are about 1.0, and their refractive indexes are of theorder of 1.55 at 20 0. Their dielectric constant throughout the rangefrom 100 cycles to 3 megacycles is about 2.5, while the power factor forthe same frequencies is less than 0.001.

Bald dimers are valuable as plasticizers. especially for syntheticresins of the vinyl type, havbeen used with particular eflectiveness inplasticizing polystyrene. They are advantageous when combined withresins or other substances that are used where their insulatingproperties are important, in view of the exceptional electricalqualities of said dimers.

The dimers are also useful as impregnants for capacitors, as cable oils,and in similar uses where their electrical qualities are exceptionallyvaluable. They are suited for use as heat-exchange liquids, andconstitute desirable transformer oils. They are miscible withsubstantially all standard organic solvents except the lower alcohols,and are of importance as solvents. These characteristics are distinctiveof the dimers obtained by this process; and a feature of the inventionis the production of said dimers having a purity substantially higherthan has heretofore been 4 obtained and unexpected characteristics whichwere heretofore unknown.

The reaction details which have been given are on the basis ofatmospheric pressure: and changes in pressure will vary the reactionconditions in known manner. The percentages given are by weight. It isunderstood when referring generally to dimers that the dimers of thedescribed alpha-alkyl para-alkyl styrenes are indicated.

While certain preferred tion have been disclosed, tended to be by wayforms of the inventhis disclosure is inof illustration and notlimitation, since numerous other variations apparent to those skilled inthis art can be made without departing from the-invention as set forthin the claims We claim:

1. The method of dimers of alpha-alkyl comprises the steps alpha-alkylpara-alnl than five carbon atoms making substantially pure para-alkylstyrenes which of mixing a monomeric styrene having not more in eitherthe alpha or the para substituents at temperatures in the range betweenC. and the boiling point of the monomer. with between and 10% by weightof previously activated fuller's earth. said fuller's earth having beenactivated by heating at temperatures between 200 C. and 400 C.,maintaining the mixture within said temperature range until therefractive index is substantially stabilized, removing the fuller'searth and separating the dimer from the remaining constituents. 2. Themethod set forth in claim 1 in which the fuller's earth is floridln.

3. The method set forth in claim 1 in which the fuller's earth isactivated by heating at temperatures between 200 C. and 400 C. until substantially anhydrous.

4. The method set forth in claim 1 in which the fuller's earth isactivated by heating between 325 C. and 875 C. until substantiallyanhydrous.

5. The method set forth in claim 1 in which the monomer is mixed withbetween 2% and 5% of the fuller's earth.

6. The method set forth in claim 1 the fullers earth is floridin, usedin proportions between 2% and 5%.

7. The method set forth in claim 1 in which the styrene compound isalpha-methyl paramethyi styrene.

8. The method set forth in claim 1 in which the styrene compound isalpha-methyl para-ethyl styrene.

ARTHUR. J. WARNER. THEODORE H. TALBOT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS in which OTHER REFERENCES Bell 5, 654 (1932). (C01in Division 6.)

